1. FIELD OF THE INVENTION
The present invention relates to a data communication method and a communication system using a communication apparatus which transmits or receives data between a plurality of terminals, and more particularly, to a data communication system which utilizes the data communication method and apparatus to perform a wireless data communication by the polling/selecting method.
2. RELATED ART
The conventional wireless data communication apparatus, in which data communications with a main unit are performed by a plurality of terminals, generally utilizes the polling/selecting method. In the polling method, the main unit periodically performs polling for a data transmission on each terminal. In the case where a terminal affirmatively responded to the polling, the main unit receives the data which was transmitted from the terminal. In the selecting method, the main unit periodically performs selecting for a data reception on each terminal. In the case where a terminal affirmatively responds to the selecting, the main unit transmits the data to the terminal. Thus, the main unit in the conventional wireless data communication system periodically executes the aforementioned polling/selecting processing regardless of the operational status of the terminal since the main unit cannot grasp the status of each terminal. For example, in the case where the power source of the terminal is set to OFF, time for polling/selecting or waiting time for a response from the terminal will be wasted. Thus, in the conventional wireless data communication system, there is the drawback such that efficiency of the data processing is decreased since unnecessary data communications processings are executed and waiting time for polling/selecting for the rest of terminals becomes longer.